The present invention generally relates to a method of manufacturing optical fiber, and more particularly relates to manufacturing optical fiber in a fiber draw production system to achieve desired bandwidth characteristics.
Conventional manufacturing processes for producing optical fibers typically include drawing optical fiber from a heated glass preform in a draw furnace, cooling the drawn fiber, and coating the fiber after it has sufficiently cooled. The bandwidth of multimode (MM) fiber (MMF) is generally limited by inter-modal chromatic dispersion. To minimize the inter-modal chromatic dispersion, MM fibers are typically designed with graded index α-profiles. For an optimum bandwidth, the parameter α which is the refractive index profile variation typically is at a value near 2 for a typical drawn fiber. However, the bandwidth may be sensitive to profile changes from its optimum shape and departure from the optimum α parameter may result in a significant drop in the bandwidth. Achieving the optimum bandwidth requires precise profile control; however, it is generally difficult to make an optimum α-profile due to the refractive index measurement for a given preform generally not having the precision required to determine accurately the α value, and the draw tension induced stress can change the refractive index profile. Thus, typically optimum draw tension cannot be accurately predicted due to inaccuracy of the profile measurement for a given preform. If the index profile in the fiber has a significant error in the α parameter, the fiber bandwidth may be low, which may result in poor selects for high bandwidth fibers.